Not applicable.
The present invention relates to structures and support members in general, and more particularly to structures which may be readily erected from a compact configuration to an expanded configuration of substantially greater stiffness.
Conventional building materials such as plywood, wood timbers, steel trusses, concrete blocks, etc., can be specified to give the desired stiffness and load carrying capacity for a particular project. These conventional materials are adequate for applications where transportation costs are low. A wide variety of engineered materials have been developed which maximize the stiffness to weight ratio for applications where structural weight is the chief concern. For example, interior structures in aircraft and spacecraft should be as lightweight as possible for a desired stiffness. Moreover, the transport costs are generally a function of mass and the additional cost of a high stiffness-to-weight-ratio building member can be justified. Corrugated cardboard, foam core board, and honeycomb board are examples of some stiff but lightweight planar building members.
Yet mass is only one constraint limiting transport capacityxe2x80x94the other is volume. A honeycomb board, for example, demonstrates exceptional stiffness for its weight, with the result that most of the volume of the honeycomb board is air. On board aircraft, marine craft, and land vehicles, cargo-carrying volume is usually strictly limited. In instances where it is necessary to move building materials rapidly or to have quantities of building materials readily on hand with minimal storage capacity, it would be desirable to have stiff building materials which are easy to work with, of adequate strength, and which occupy minimal volume during shipping and storage.
The structural member of this invention in a preferred embodiment has two parallel sheets, a top member and a bottom member, which are connected together by a plurality of wing members. Each wing member has a center segment which is hinged to the top member and to the bottom member about parallel hinge axes. At least one wing protrudes from each center segment and is biased to project out of the plane defined between the hinge axes of the center segment. For example, the wings may be formed as curved or angled extensions from the center segment in a plastic or metal spring. The structural member is transformable from a first, collapsed, condition to a second, expanded condition. In the collapsed condition, the top member is close to the bottom member, with the wing members compressed between the two sheets and the wings distorted out of their relaxed positions. In the expanded condition, the top member is spaced from the bottom member and the wings, in their relaxed positions, project out of the planes of the center segments and confer substantial stiffness to the structural member. The wing members may be fabricated as independent units, or may be constructed as a series of biased wings on continuous strips of material.
The structural members may be retained in the collapsed condition by an adhesive binding or tape which wraps the edges of the structural member and extends from the top member to the bottom member. A quick release cord or wire may be positioned beneath the tape such that the structure may be expanded without the use of tools. Locking tabs may be formed on one of the top or bottom members to contribute to retaining the structural member in its expanded erect configuration. The collapsed structural member may be stored as sheets, or rolled up into rolls. The structural members may be used in military and remote construction applications, for example as short bridges, roof members, foxhole liners, furniture, elevated walkways, shelters, flooring, ladders, stairs, ramps, and craft.
It is a feature of the present invention to provide a structural member which is readily transformed from a collapsed condition to an expanded condition.
It is another feature of the present invention to provide a structural member which, when expanded from a collapsed condition, does not have a tendency to return to the original collapsed condition.
It is an additional feature of the present invention to provide an expandable structural member which may be stored in rolls.
It is also a feature of the present invention to provide a structural member which may be fabricated from a wide range of materials.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.